1. Field of the Invention
This invention relates to an apparatus for driving a pile into the soil at a considerable depth under water, and features a ship provided with means for mounting and lowering a pile to be driven into the soil or sea bed, as well as a drop-hammer, which can be lowered upon or with said pile.
2. Description of the Prior Art
A similar apparatus is known from the Dutch patent application No. 6808617, laid open for public inspection.
In the not pre-published Dutch patent application No. 7408710 corresponding to U.S. Ser. 588,554, the pile to be driven into the soil is suspended from cables and lowered together with the drop-hammer placed on it. As soon as pile and drop-hammer have reached the soil the driving can start. This is attended with impact-loads in the cables which keep the assembly of the pile and drop-hammer in an upright (vertical) position. To meet this problem it is proposed in Dutch patent application No. 7410905, which is an addition to patent application No. 7408710, to freely and movably guide the drop-hammer and the pile in a frame suspended from the hoisting means for the drop-hammer, which frame itself is guided upon cables from which the pile is suspended. When reaching the bottom the hoisting cable, which is coupled to the frame, is tensioned, after which the driving can start. This frame exerts a stabilizing effect upon the pile, which is necessary in the starting phase of the drive because the pile, which has not yet penetrated into the soil, tends to tip or overturn. This stabilizing effect is based on the fact that the pile and guide-frame tend to move in arcs of a circle, moving away from each other. As the upper end of the pile has been guided in the frame, such movement is not possible. If the upper end of the pile deviates from the vertical position then the frame must follow this deviation, but the frame resists such deviation because by means of its suspension it wants to maintain a vertical position. The correcting couple which is exerted is relatively small, and with piles of great length this solution cannot be used.
In Dutch patent application No. 7505975 it is proposed to lower the drop-hammer by cables after lowering the pile, with the aid of a guide-sleeve connected to the drop-hammer, enclosing the upper end of the pile, and guided cables which are tensioned between the vessel and a body lowered and resting upon the bottom of the sea.